2-Ethylhexanol is used in large quantities as an esterification component, e.g. for the preparation of dioctyl phthalate as a plasticizer for PVC. 2-Ethylhexanol is made by alkali-catalyzed condensation of n-butyraldehyde to yield the unsaturated aldehyde, 2-ethyl-hex-2-enal, which is then hydrogenated to yield the desired 2-ethylhexanol.
Various processes for the production of n-butyraldehyde are known. It is also known that n-butyraldehyde will contain, as an impurity, isobutyraldehyde and that oligomers of isobutyraldehyde will be present due to hydroformylation. These impurities will, if not removed, lead to the formation of 2-ethyl-4-methyl-pentenal during the preparation of 2-ethyl-hex-2-enal. The 2-ethyl-4-methyl-pentenal is then hydrogenated to the alcohol, 2-ethyl-4-methyl pentanol during the preparation of 2-ethylhexanol and cannot be economically removed.
2-Ethyl-hex-2-enal is prepared by the alkali-catalyzed aldol condensation of n-butyraldehyde.
2-Ethylhexanol is prepared by the hydrogenation of 2-ethylhex-2-enal (oxo successive product). In this process hydrogenation can occur both in the gaseous phase (DE-AS 11 52 393) and in the liquid phase (DE-AS 19 49 296). In these processes higher catalyst loads can generally be achieved in the liquid phase due to improved dissipation of heat.
2-Ethylhexanol is used for production of the plasticizer, di-2-ethylhexyl phthalate and for many other uses. The presence of even minor amounts of contaminants will reduce purity and may affect the end use and even render it unacceptable. Accordingly, there exists a need in the art to reduce the quantity of contaminants in general and 2-ethyl-4-methyl pentanol in particular.